High-concentration electrolytes for lithium metal batteries operating at high temperatures

doi:10.21203/rs.3.rs-4994418/v1

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High-concentration electrolytes for lithium metal batteries operating at high temperatures

https://doi.org/10.21203/rs.3.rs-4994418/v1

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Commercialized electrolytes for lithium-metal batteries have a maximum temperature restriction of 60°C, which significantly restricts the use of these batteries in situations with greater temperatures. In this paper, we study the construction of a high-temperature electrolyte system for lithium metal batteries, using 0.5 M LiODFB-EC/EMC (3:7) as the basic electrolyte system, and 1, 2, and 3M LiTFSI were added to form electrolytes with different concentrations, to investigate the effect of LiTFSI concentration on lithium-metal batteries. The mixed lithium salts used in this system are lithium bis(trifluorosulfonyl) imide (LiTFSI) and lithium difluoro-oxalate-borate (LiODFB), with ethylene carbonate (EC) and ethyl methyl carbonate (EMC) as the mixed solvent systems. Additionally, we study the electrochemical performance at 45°C and 70°C. The best battery performance was achieved with batteries built with 3.0M LiTFSI/0.5M LiODFB electrolyte. The LiCoO₂/Li discharge performance After 500 cycles, the battery's discharge-specific capacity was 117.8 mAh/g, and its capacity retention rate was 82.8%. Better than previous concentration electrolyte systems, the battery constructed with this electrolyte has a greater discharge-specific capacity and cycle stability at 70°C.

high-temperature lithium metal batteries. lithium bis(trifluorosulfonyl)imide (LiTFSI). lithium difluorooxalate borate (LiODFB). highly concentrated electrolyte. solid-state electrolyte film

Due to its shallow redox potential (-3.04v versus standard hydrogen potential) and ultra-high theoretical specific capacity (3860 mAh g^− 1), high energy density can be achieved by assembling lithium metal anodes (LMAs) with a wide range of high-voltage cathode materials[1]. Lithium Metal Batteries (LMBs) are widely used in a wide range of industrial sectors because of their advantages of high energy density and long-cycle stability [2]. The current high-temperature limit of the commercialized electrolyte suitable for LMBs is 60°C, which severely limits the application of LMBs in higher-temperature scenarios. At the same time, LMBs also face some application challenges, such as higher reactivity of lithium to the electrolyte and more severe side reactions compared to traditional graphite anodes, resulting in lower Coulombic Efficiency (CE) of lithium anodes. The volume change of lithium is much larger than that of graphite, which results in the formation of a solid electrolyte phase (SEI) on the surface of the lithium anode, which is repeatedly generated and decomposed during the cycling process, which can lead to continuous depletion or even exhaustion of the electrolyte[3–4]. Lithium metal anodes produce lithium dendrites during cycling, which can puncture the diaphragm, leading to short circuits and possibly fires [5–7].

In recent years, researchers have found that when the salt concentration in the electrolyte rises to a certain threshold, the chemical structure of the solution undergoes drastic changes, with a decrease in free solvent molecules and solvent-separated ion pairs (SSIP) and an increase in the concentration of contact ion pairs (CIP) and aggregates (AGG); these are referred to as high-concentration electrolytes[8–10]. Compared to conventional electrolytes, highly concentrated electrolyte systems have excellent physical properties such as high Li transfer number[11–12], fast electrode response, and resistance to Al collector corrosion[13–17]. Concentrated electrolytes are thermally stable. Commercial diluted electrolytes mainly use carbonate-based solvents, which can easily side-react with lithium to produce a loose SEI film on the surface and grow dendrites that can easily puncture the diaphragm, leading to short-circuiting of the battery. Linear carbonates such as DMC and EMC are highly volatile and flammable[18–20]. The change of solution structure in concentrated electrolytes reduces the number of free solvent molecules and the contact with lithium [8][21–22]. The concentrated electrolyte can form an anion-derived SEI passivation film on the LMA surface, which is denser and more stable than the SEI formed by the conventional electrolyte. Lee et al. formulated 4 M LiFSI in PC/FEC (93:7 v/v). They utilized the well-coordinated structure of Li⁺-FSI⁻solvent clusters and FEC-optimized SEI for Li||NCM811 full batteries to achieve flame-retardant, high-voltage LMBs with excellent electrochemical performances (energy densities up to 679 Wh kg^− 1 and stable capacity at elevated temperatures) [23–24]. In addition, concentrated electrolytes can further reduce flammability by using a range of nonflammable solvents such as phosphates or sulfones. Still, such solvents have traditionally been difficult to apply to LMBs due to their high reactivity with LMA[16][24–26]. Zhang et al.[27] used a high concentration of lithium salt, LiFSI, and a nonflammable solvent, trimethyl phosphoric acid (TMP), to prepare different concentrations of electrolytes and to measure TGA. they found that the thermal stability of the electrolyte increased significantly with increasing concentration. In addition, 4 M LiFSI in TMP was used as a nonflammable electrolyte for Li||LiFePO₄ batteries, and there was no significant decrease in capacity over 90 cycles. Shiga et al[28] used a self-extinguishing concentrated fluorinated phosphate electrolyte LiFSI-TEEP (1:2M) in a high-pressure Li||LiNi_0.8Co_0.15Al_0.05O₂ half-cell. Thermal stability was improved by the multiple effects of a highly concentrated, thermally stable phosphate and solvent fluorination. The battery capacity was maintained at about 80% after 100 cycles at 80°C, and the electrolyte could not be ignited at 700°C, improving the safety of LMB.

LiTFSI has high thermal stability, easy ionizability, and good film-forming properties. However, LiTFSI is highly corrosive to aluminum foil collectors, so it usually needs to be mixed with other lithium salts. Wang et al[29]. investigated the effect of 1 M LiPF₆ + LiTFSI-EC/EMC (1:1) electrolyte on the performance of LiNi_1/3Mn_1/3Co_1/3O₂ graphite full cell and found that the use of LiTFSI reduced the charge transfer resistance and self-discharge rate and gas precipitation under high-temperature storage. charge transfer resistance, self-discharge rate, and gas precipitation under high-temperature storage.LiODFB has a high solubility in linear carbonate solvents, and in addition, it can form a stable SEI film on the graphite negative electrode. Li et al[30]. demonstrated that mixing LiODFB with LiTFSI in a certain ratio can effectively inhibit the corrosion of LiTFSI on aluminum foil collector during charge/discharge at room temperature. In this paper, LiODFB is added as a common salt in the LiTFSI-based electrolyte, and the concentration of LiTFSI in the electrolyte is increased to increase the content of TFSI⁻ in the solvated sheath, to investigate the effect of different concentrations of electrolyte on the high-temperature performance of LMB.

Preparation of different electrolytes

Table 1 displays the contents of the electrolyte that was utilized in the experiment. Dongguan Koluder Experimental Equipment Technology Co. was the supplier of the reagents and lithium salts that were used. A glove box with an argon environment with H₂O and O₂ levels less than 0.1 ppm was used for conducting the research. The electrolytes that were utilized in the particular tests are listed in Table 1 below.

Table 1

Electrolyte system used in the experiment
number	LiTFSI / mol·L^− 1	LiODFB / mol·L^− 1	Solvent Ratio
E1	1.0	0.5	EC:EMC = 3:7 v/v
E2	2.0	0.5	EC:EMC = 3:7 v/v
E3	3.0	0.1	EC:EMC = 3:7 v/v
E4	3.0	0.3	EC:EMC = 3:7 v/v
E5	3.0	0.5	EC:EMC = 3:7 v/v

Electrochemical performance characterization

This experiment uses the LAND CT2001A battery testing equipment to cycle and multiply the batteries. Before starting the 45/70℃ cycle and multiplier test, the battery was first charged and discharged 3.5 times at 0.1C to make the battery in a full-charged state. The battery was then put into the battery fixture in the high-temperature box, and then stood still for 30 min, discharged first, and then proceeded to the normal charging and discharging procedures. Cyclic test of Li/Cu half battery: current density is 1mA/cm², capacity is 1mAh/cm2, discharging then charging in the test process, discharging and charging in the test process, the cut-off time is 1h and a charging cut-off voltage of 1V. The discharge, and charging deadlines are 10, 5, 2, 1 and 0.5 h. The cycling test of LiCoO₂/Li battery: the current density is 1C, the voltage range is 2.7-4.2V; the multiplication test current density is 0.2, 0.5, 1, 2, and 5C, and the voltage range is 2.7-4.2V.

This paper used a Chenhua 660e electrochemical workstation with a voltage range of 2.5-5 V and a sweep rate of 1 mV/s. Cyclic voltammetry (CV): CV test was performed on Al/Li half-cells with a voltage range of 2.5-5 V and a sweep rate of 1 mV/s. CV test was performed on Li/Cu half-cells with a voltage range of 0–3 V and a sweep rate of 1 mV/s. CV test was performed on LiCoO₂/Li half-cells with a 2.5–4.5 V voltage range and a sweep rate of 1 mV/s. CV test for LiCoO₂/Li cell, voltage range: 2.5–4.5 V; sweep rate: 1 mV/s. Electrochemical impedance test (EIS): Chenhua 660e electrochemical workstation, frequency: 105 − 0.1 Hz; amplitude: 5 mV.

Timed current method test instrument: Tatsunghwa 660e electrochemical workstation, voltage: 4.2 V; time: 12h. Scanning electron microscope (SEM): working voltage: 5 kV. Transmission electron microscope (TEM): the dried pole piece was ultrasonicated in the EMC, and then dropped onto a 200-mesh copper mesh of 3 mm in diameter with a capillary tube to test its morphology. X-ray Photoelectron Spectroscopy (XPS): X-rays are used to irradiate the samples so that the inner electrons or valence electrons of the atoms or molecules are stimulated to be emitted, and the chemical information such as the elemental species and valence state of the samples are inferred from the distribution of the photoelectrons generated. The experiments were performed using Advantage software for peak splitting.

Al/Li half-cell corrosion test

There was current augmentation at 3.1 V during the first cycle of all electrolytes, as shown in Fig. 1(a-e). The current intensity of each electrolyte's CV curve decreased and showed good overlap as the number of cycles increased. Among these, no corrosion current was produced in the CV curves despite the LiODFB levels in the E3 and E4 electrolytes being below 0.3 mol/L or less. As a result, it is thought that raising the LiTFSI concentration in the electrolyte can partially prevent the corrosion of aluminum foil.

To confirm once more that increasing the LiTFSI concentration can stop aluminum foil from corroding. Al/Li half-cells with various electrolyte systems underwent timed current tests at 70°C. The cells were maintained at a voltage of 4.2 volts for 12 hours, during which the current change was monitored. According to Fig. 1(g), E3 electrolyte takes approximately 5 hours to produce a corrosion current at 4.2V, whereas the E4 electrolyte requires just 10 hours to produce a corrosion current. This suggests that while raising the LiTFSI concentration in the electrolyte will partially stop the corrosion, it cannot stop the electrolyte from corroding the aluminum foil.

Stripping/plating test for lithium metal anode

To further confirm the improvement in interfacial stability, the CE of Li/Cu cells with E1, E2, and E5 electrolytes was measured; the results are displayed in Fig. 1(f). Both cells underwent two cycles of 0 to 2.5 V at a current density of 0.05 mA/cm² to stabilize and activate the interfacial layer before testing. Li was initially deposited on the Cu electrode at a current density of 1 mA/cm² with a capacity of 1 mAh/cm² and then peeled from the Cu foil at a cutoff voltage of 1 V and 1 mA/cm². For the Li/Cu cell with E5 electrolyte, the CE values exhibit modest changes in 50 cycles. On the contrary, for the Li/Cu cell containing E1 and E2 electrolyte systems, there are significant fluctuations at the start of the cycle, indicating that the cycling stability of the E1 and E2 electrolyte systems has not improved despite an increase in the concentration of lithium salts, which could be due to electrolyte formation on the electrode surface. The SEI coating on the electrode surface is not sufficiently stable.

The constant current discharge curves of Li/Cu half-cells built using various electrolytes are displayed in Fig. 1(h). It makes evident that each electrolyte's overpotential and plateau potential vary significantly from one another. Among these, the difference between the overpotential and the plateau potential is the nucleation overpotential of the lithium ion. E5 electrolyte has the shortest nucleation overpotential of the three electrolytes, while E1 electrolyte has the biggest nucleation overpotential. This suggests that as the concentration of electrolyte increases, the nucleation overpotential progressively lowers. Lithium has a reduced nucleation and growth barrier when its nucleation overpotential is lower. As a result, the E5 electrolyte's lower nucleation overpotential is beneficial to lithium metal battery performance at high temperatures.

Figure 1(i) depicts the cyclic voltammetry test plots of Li/Cu cells with varying electrolytes. The decreased peak at 1.7 V can be attributable to the decomposition of LiODFB, and because the LiODFB content in the three electrolytes is the same, the peak currents here do not differ significantly. The peak at 1.1 V corresponds to the decomposition of LiTFSI. The decomposition current of LiTFSI in E5 electrolyte is greater than that of the other two electrolytes, indicating that E5 electrolyte contains more TFSI⁻anions in the lithium-ion solvation layer. The peak currents of the E1 and E2 electrolyte systems, on the other hand, are quite close, indicating that the amount of TFSI⁻ anions present in the lithium-ion solvation layer is not significantly different between these two concentration electrolyte systems.

The cycling curves of Li/Li symmetric cells built with various electrolytes are displayed in Fig. 1(j) The fixed capacity and current density were set to 1 mAh/cm² and 1 mA/cm², respectively, as illustrated. The symmetric battery with E5 electrolyte was able to cycle steadily for more than 200 hours at 70°C, however the Li/Li symmetric battery with E1 and E2 electrolytes was extremely unstable and difficult to cycle for more than 200 hours, similar to the Li/Cu battery. The distinct SEI coatings that develop on the electrode surfaces of these three electrolytes may be the reason for the glaring differences in their cycling performance.

Comparing the Magnification Performance of Li/Li symmetric cells with various electrolytes reveals, as seen in Fig. 1(k), that the cells overpotentials rise at current densities between 0.1 and 2 mA/cm². This is because an increase in current density causes a large number of ions to be adsorbed at the electrode/electrolyte interface, resulting in a rapid decrease in the electrolyte ion concentration at the interface, an increase in concentration polarization, and a subsequent increase in the overpotential. Through a comparison of the battery's overpotential at 1 mA/cm² and 2 mA/cm² current densities with various electrolytes, it can be observed that E5 electrolyte has the lowest overpotential. For large current intensities, this suggests that E5 electrolyte performs better multiplicatively and exhibits less polarization. The efficient electrolyte film production on the electrode surface and the quick detachment/embedding of lithium ions during high current density charging and discharging, which put more strain on the mechanical strength of the SEI layer, may be connected to the good multiplicity performance.This suggests further that high-temperature lithium metal battery performance is improved by the E5 electrolyte.

The impedance profiles of several electrolytes following a cycle from 30 to 70 degrees Celsius are displayed in Fig. 2(a-c). The Li/Li symmetric cell with E5 electrolyte has the lowest impedance, as can be seen in the image. Arrhenius' law is used to compute Ea in Fig. 2(d). The E5 electrolyte system's activation energy (64.98 kJ/mol) is less than that of the E1 and E2 electrolyte systems (66.95 and 66.25 kJ/mol). The kinetics in the E5 electrolyte system are better, according to this investigation.

Electrochemical performance test of LiCoO₂/Li full battery

Table 2

Cyclic discharge specific capacity of different electrolyte systems
electrolyte	First discharge specific capacity mAh/g	200th discharge specific capacity mAh/g	Specific capacity of the 500th discharge mAh/g	capacity retention %
E1	144.1	Cannot complete 200 cycles	Cannot complete 500 cycles	-
E2	143.3	Cannot complete 200 cycles	Cannot complete 500 cycles	-
E5	142.2	133.6	117.8	82.8%

LiCoO₂/Li constructed with various electrolyte systems underwent charge/discharge cycling testing; Fig. 2(e) presents the findings. The charge-discharge cycle performance of LiCoO₂/Li batteries constructed with various electrolyte systems was investigated at 70°C. The first discharge-specific capacities of the three electrolytes are E1-144 mAh/g, E2-143.3 mAh/g, and E5-142.2 mAh/g, respectively, as indicated in Table 2. As the concentration of the electrolyte increases, the specific capacity of the first discharge of the electrolyte decreases due to the negative correlation between the concentration of the electrolyte and conductivity After 500 cycles, the LiCoO₂/Li full cell in the E5 electrolyte system had a discharge specific capacity of 117.8 mAh/g, while the LiCoO₂/Li full cell in the E2 electrolyte system demonstrated a clear capacity decline after 100 cycles until the cell failure. This could be because the CEI and SEI film components formed by this electrolyte system on the electrode surface are not stable enough and dissolve into the electrolyte at high temperatures, causing the electrolyte to constantly come into contact with the electrode surface, resulting in the battery's sudden failure. Furthermore, the E1 electrolyte performs worse at high temperatures. The capacity retention rate of the LiCoO₂/Li complete battery with E5 electrolyte remained 82.8% after 500 cycles. It indicates that the cycle life and capacity retention of lithium metal batteries at 70°C can be enhanced by the E5 electrolyte system. This significant enhancement of the overall battery performance indicates even more how well the E5 electrolyte system works with LiCoO₂ cathode materials and lithium metal anodes.

Plots illustrating the multiplicative performance of cells built with various electrolytes are displayed in Fig. 2(f). It is evident from the Fig. 2(f) that different electrolytes have varied discharge-specific capacities for LiCoO₂/Li complete batteries. With average capacities of 140.4, 136.5, 135.5, 132.3, and 124.9 mAh/g at multiplicities of 0.2, 0.5, 1, 2, and 5 C, respectively, the cell containing E5 electrolyte demonstrated the best high-temperature multiplicity performance. After cycling at a conventional multiplicity of 1 C, the cell's average specific capacity of discharge was 133.5 mAh/g, indicating that this electrolyte system has less capacity damage to the battery after cycling at a large multiplicity. In contrast, the specific capacity of E1 and E2 electrolytes showed some degradation after cycling at various multiplicities, particularly after large multiplicities and the capacity degradation was severe with 1C cycling. This could be attributed to the creation of an unstable interfacial coating of electrolyte on the electrode surface, resulting in continual electrolyte breakdown and a reduction in the battery's discharge-specific capacity.

The cyclic voltammetric test results of LiCoO₂/Li cells assembled with different electrolytes at 70°C are shown in Fig. 2(g-i). First, from the peak potential difference, the peak current ratios of different electrolyte-assembled batteries in the first turn are all greater than 1. This is due to the oxidative decomposition of the electrolyte to form a film on the electrode surface. With an increase in scanning turns, the peak current ratio of the E5 electrolyte approaches one, while the peak current ratios of the E1 and E2 electrolytes remain greater than one, indicating that the two electrolytes continue to decompose, which is detrimental to the battery's cycling performance. Comparing the ΔEp on the CV curves of various electrolytes reveals that the ΔEp of the E1 and E2 electrolytes increases as the number of sweeps increases. This indicates that the battery's polarization phenomenon is intensified, which decreases the battery's capacity. The E5 electrolyte creates a more dense and uniform interfacial coating that can effectively protect the electrodes and slow down the electrolyte's breakdown because it participates in the interfacial reaction with a high concentration of lithium salts. The battery's service life can be extended and its cycling stability can be enhanced by this protection method.

The electrochemical performance of LiCoO₂/Li cells was shown to be considerably impacted by varying electrolyte concentrations, as demonstrated by testing the cells using the electrochemical impedance method. Figure 2(k-l) presents the findings. It can be seen that the change of electrolyte concentration will directly affect the performance in the battery, which provides an important reference for further research on the relationship between electrolyte concentration and battery performance The E1 electrolyte's impedance profile is displayed in Fig. 2(j) following 25 and 50 cycles at a high temperature. It is evident from this profile that the impedance rises as the number of cycles increases, suggesting a gradual thickening of the interfacial film. The E2 electrolyte system continues to exhibit an increase in impedance after 25 and 50 cycles, as shown in Fig. 2(k). This could be because the battery contains a lot of organic components in the interfacial membrane during the high-temperature cycling process at 70℃, and the organic components are easily dissolved out of the electrolyte, causing the electrode to re-contact with the electrolyte and causing a side reaction. After extensive cycling, the E5 electrolyte system's battery impedance shows no discernible change, suggesting that the electrode is progressively thickening. The E5 electrolyte system's battery impedance does not noticeably change after extended cycling, indicating that the electrolyte's interfacial coating on the electrode surface is sufficiently stable.

Physical Characterization of LiCoO₂/Li Cells

Figure 3 reveal the morphology of the pole piece after cycling at 70°C in different concentration electrolyte systems.As shown in Fig. 3(d-f), after 100 charge/discharge cycles of LiCoO₂ cathode in E1, E2, and E5 electrolytes, the E1 and E2 electrolytes form a loose and uneven interfacial film on the cathode's surface, resulting in partial exposure of the cathode material and accelerating the electrolyte's continuous decomposition. On the contrary, E5 electrolyte generates a dense and stable interfacial coating, effectively inhibiting the electrolyte's oxidative breakdown. Therefore, the battery containing E5 electrolyte has better high-temperature stability, which is consistent with the results obtained from the electrochemical performance.

The results obtained by comparing TEM images of different electrolytes after 100 cycles are congruent with the SEM photos. Figure 3(a) demonstrates that the E1 electrolyte generates a thick and non-uniform interfacial coating on the electrode surface, which reduces the cell's high-temperature cycling stability. A constant side reaction between the electrode and the electrolyte will result from the E2 electrolyte's formation of a thick interfacial coating and clear interfacial fracture on the electrode surface, as seen in Fig. 3(b). Furthermore, after 100 cycles in the E5 electrolyte system, a consistent and thick film layer was seen on the positive electrode's surface, indicating that the battery made with this electrolyte system has good stability at high temperatures.

Figure 4 shows the analysis of the interfacial composition after cycling in the electrolyte system with different concentrations. After 100 cycles at 70°C, the cathode's surface was examined using X-ray photoelectron spectroscopy (XPS) to identify the elements of the interfacial film that various electrolyte systems had developed on the cathode material's surface. Two peaks can be observed in the Li 1s spectrum, the peak at 55.4 eV corresponds to Li₂CO₃ produced by the decomposition of LiODFB in the electrolyte, and the peak at 56.1 eV corresponds to LiF produced by the decomposition of LiTFSI in electrolyte. By comparing the three electrolytes, it can be observed that the content of LiF in the CEI film increases with the rise of the concentration of LiTFSI in the electrolyte, which suggests more TFSI-anions are involved in the interfacial reaction. Comparing the F1s spectra further, we find that LiF corresponds to the peak at 685.2 eV, while -CF₂/-CF₃ is responsible for the peak at 688.2 eV. Compared to the E2 and E1 electrolyte systems, the electrode surface of the E5 electrolyte has a higher LiF content. While the LiTFSI concentration in E5 electrolyte is higher than that in E2, the peak intensities are close to each other, which suggests that there is more TFSI⁻ involved in the film-forming reaction in the E5 electrolyte, which is in agreement with the results of Li1s spectra. Comparing the peak intensities of -CF_2/-CF₃, it can be observed that the peak intensities of the E5 and E2 electrolyte systems are much smaller than that of the E1 electrolyte system, which indicates that more organic compounds are formed in the E1 electrolyte system.

As demonstrated by the findings, increasing the quantity of LiTFSI in the lithium-ion solvation layer and the number of inorganic components in the CEI/SEI membrane both enhance the high-temperature performance of lithium metal batteries. Consequently, by raising the concentration of LiTFSI in the electrolyte, the impact of the high-temperature performance of lithium metal batteries in various concentration electrolyte systems is examined in this paper. Through the corrosion experiments on Al/Li half batteries assembled by different concentration electrolyte systems, it is found that increasing the concentration of LiTFSI in the electrolyte can alleviate the corrosion of aluminum foil by the electrolyte in a short period, but it can't completely inhibit the corrosion of aluminum foil, so it is also necessary to add a certain amount of LiODFB in the electrolyte system, and it can be seen through the experiments that the concentration of LiODFB needs to be controlled at 0.5 M when the electrochemical performance of the battery at 70℃ is the best. At 70°C, Li/Cu half-cells and Li/Li symmetric cells with different electrolyte systems showed different cycle stability. Among them, the E5 (3.0 M LiTFSI + 0.5 M LiODFB -EC/EMC (3:7)) electrolyte system has the best cycling stability, and the Li/Cu half-cells can be stably cycled for 50 times, and the Li/Li pair cells can be cycled for more than 200 h. The Li/Cu half-cells and Li/Li symmetric batteries have the best cycling stability. The LiCoO₂/Li full batteries containing different electrolyte systems were cycled at 70℃. The full battery assembled with E5 electrolyte system showed more excellent cycling performance, with a capacity retention rate of 82.8% after 500 cycles at a high temperature of 70℃.It shows that the electrolyte system is not only compatible with the lithium metal anode but also has good compatibility with the cathode LiCoO₂. Characterization of the surface morphology and components of the cathode material after 100 cycles reveals that the electrolyte system forms a uniform, dense, and LiF-rich interfacial film on the surface of the electrode, which is the main reason for the stable cycling of the battery at high temperatures.

Acknowledgements

This work was supported by the Program of Science and Technology International Cooperation Project of Qinghai Province (No.2022-HZ-809). Qinghai National University Student Innovation and Entrepreneurship Training Program Project (No.2024-DCXM-43)

Author contribution

L.L. and J.H. wrote the main manuscript text. X.Y.prepared Figs.1. H.Q. prepared Figs. 2. L.Z. provided the experimental conditions. All authors reviewed the manuscript.

Data availability

No datasets were generated or analysed during the current study.

Competing of interest

The authors declare no competing interests

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You are reading this latest preprint version

High-concentration electrolytes for lithium metal batteries operating at high temperatures

Status:

Version 1

Abstract

Figures

Introduction

Materials and methods

Preparation of different electrolytes

Electrochemical performance characterization

Results and Discussion

Al/Li half-cell corrosion test

Stripping/plating test for lithium metal anode

Electrochemical performance test of LiCoO₂/Li full battery

Physical Characterization of LiCoO₂/Li Cells

Conclusion

Declarations

References

Additional Declarations

Status:

Version 1

High-concentration electrolytes for lithium metal batteries operating at high temperatures

Status:

Version 1

Abstract

Figures

Introduction

Materials and methods

Preparation of different electrolytes

Electrochemical performance characterization

Results and Discussion

Al/Li half-cell corrosion test

Stripping/plating test for lithium metal anode

Electrochemical performance test of LiCoO2/Li full battery

Physical Characterization of LiCoO2/Li Cells

Conclusion

Declarations

References

Additional Declarations

Status:

Version 1

Electrochemical performance test of LiCoO₂/Li full battery

Physical Characterization of LiCoO₂/Li Cells